$(document).ready(function() {
    $("#formulier").validate({
        rules: {
            login: {
                required: true,
                minlength: 3,
                maxlength: 20
            },
            wachtwoord: {
                required: true,
                minlength: 3,
                maxlength: 20
            }
        },
        submitHandler: function(form) {
            form.submit();
        }
    });
});